Dr Quyen Nguyen,assistant professor of head and neck surgery, developed and injected a fluorescent peptide - a protein fragment consisting of amino acids - into mice. The peptide preferentially binds to peripheral nerve tissue, making it ten times brighter than the tissue around it.

The effect occurs within two hours and lasts for six to eight hours, with no observable effect upon the activity of the fluorescent nerves or behavior of the animals.

"Of course, we have yet to test the peptide in patients, but we have shown that the fluorescent probe also labels nerves in human tissue samples," Nguyen said.

Interestingly, the technique works even in nerves that have been damaged or severed, provided they retain a blood supply - meaning it could be a useful tool when repairing injured nerves.

"The analogy I use is that when construction workers are excavating, they need a map showing where the existing underground electrical cables are actually buried, not just old plans of questionable accuracy," said co-author Roger Tsien.

"Likewise, when surgeons are taking out tumors, they need a live map showing where the nerves are actually located, not just a static diagram of where they usually lie in the average patient."

The researchers plan to carry on testing the technique in animals, and, later, people.